Enhanced Lifetime of Organic Light-Emitting Diodes Using an Anthracene Derivative with High Glass Transition Temperature

Abstract

Highly stable and efficient phosphorescent organic light-emitting diodes (OLEDs) were demonstrated by using anthracene-based hole injection buffer layer possessing high glass transition temperature. We synthesized a new anthracene derivative, 9,10-bis(3,3'-(N',N'-diphenyl-(N-naphthalene-2-yl)benzene-1,4-diamine) phenyl)anthracene (TANPA) and characterized its optical and thermal properties. It showed high glass transition temperature of 154 degrees C which could be attributed to the insertion of anthracene into the aromatic amino group with triphenylamine. We also utilized TANPA for the hole injection and transport layers in phosphorescent OLEDs. Since TANPA has high glass transition temperature, the OLEDs using this material exhibited higher operational stability compared to the device without TANPA. When we use TANPA as the hole injection layer in combination with a widely-used hole transporting material, N,N'-di(1-naphthyl)-N,N-diphenylbenzidine (NPB), the devices showed high enhancement in terms of the operational lifetime, driving voltage change, and device efficiency, originating from the electron-hole charge balance as well as good thermal stability of TANPA.